1. Field of the Invention
2. Description of the Related Art
Spinal surgery presents significant difficulties to the physician attempting to reduce chronic back pain or correct spinal deformities without introducing additional trauma due to the surgical procedure itself. In order to access the vertebrae to perform spinal procedures, the physician is typically required to make large incisions and cut or strip muscle tissue surrounding the spine. In addition, care must be taken not to injure nerve tissue in the area. Consequently, traditional surgical procedures of this type carry high risks of scarring, pain, significant blood loss, and extended recovery times.
Apparatuses for performing minimally invasive techniques have been proposed to reduce the trauma of posterior spinal surgery by reducing the size of the incision and the degree of muscle stripping in order to access the vertebrae. One such apparatus provides a constant diameter cannula which is made narrow in order to provide a small entry profile. As a result, the cannula provides minimal space for the physician to observe the body structures and manipulate surgical instruments in order to perform the required procedures. A narrow cannula is typically inconvenient if not insufficient to perform many spinal procedures, some of which require visualization of two or more vertebrae and introduction of various components and tools for applying such components.
Also, such a cannula is ineffective in procedures where the surgical site is an elongate site, extending between two adjacent vertebrae. While a certain length is needed to span the distance between the vertebrae, a corresponding width is not required in order to insert components for treatment and tools. Accordingly, either more adjacent tissue must be exposed than needed or a second cannula must be inserted. In either case, the benefits of a minimally invasive procedure are lessened.